The PHASCOPE® PMP10 DUPLEX Coating Thickness Gauge was developed by Fischer for the measurement of lacquer coatings on both zinc - plated steel and zinc - plated aluminum.

The automotive industry often requires the measurement of lacquer coating thicknesses on galvanized steel or on aluminum. Until now, such measurements required different measurement methods, instruments and probes. This required considerable effort and at times led to erroneous measurements. Now, such measurements are simpler and more reliable using the handy PHASCOPE® PMP10 DUPLEX.

Galvanized steel is used in particular in the automotive industry but also in household appliances, where the steel is painted after the forming process. This results in very good corrosion protection. The coating system consisting of zinc and lacquer is called a duplex coating. Often, it is required to maintain limits for the coating thickness. Measurements are necessary to ensure the proper thickness. The magnetic induction method that was typically used for such applications, is, however, not always ideal. It measures the total coating thickness and derives the thickness of the lacquer coating by subtracting a zinc coating thickness that is presumed to be constant. However, the latter is not constant across the surface of the component due to the manufacturing and the forming processes. For this reason, measurements of the coating thickness according to the magnetic induction method often exhibit errors. This is particularly problematic in the automotive industry when measuring a cathodic e-coating. These coatings have thicknesses between 18 and 20 µm and very narrow specification limits. Common fluctuations in the thickness of the zinc coating of between 3 and 4 µm at a nominal coating thickness of 8 µm have a significant influence on the thickness measurement of the paint coating. Thus, a measurement method and a corresponding instrument are needed that can be used to measure the actual thickness of the lacquer coating in the shop independent of the zinc coating. Suited are instruments that combine the magnetic induction and the eddy current measurement method such that the overall thickness is measured using the magnetic induction method and the zinc thickness is measured without the influence of the lacquer coating using the phase-sensitive eddy current method. The lacquer thickness is obtained by automatic difference computation. Previous instruments, such as the FISCHERSCOPE® MMS® with the DUPLEX module were, however, too cumbersome for measurements in the shop, e.g., at the line in body manufacturing.

The hand-held PHASCOPE® PMP10 DUPLEX instrument specifically satisfies the needs of the automotive industry for a portable instrument that can be used in the production for direct measurements of the coating thicknesses of zinc and lacquer independent of one another. It distinguishes itself in that the interesting lacquer coating thickness can be obtained with very high precision due to the accurate determination of the thin zinc coatings. The ergonomically designed instrument shows both the lacquer thickness and the zinc thickness on a large, backlit LCD display. Up to 20,000 measurements can be stored in a maximum of 100 applications, can be statistically evaluated and transferred to a PC via an RS232 interface for documentation purposes.

The instrument has additional advantages, particularly for the automotive industry. Without an additional measurement probe, it can measure the lacquer coating on aluminum as well by using the eddy-current method. The instrument recognizes the sheet material – galvanized steel or aluminum – automatically after placing the probe on the surface and selects the appropriate measurement method – duplex or eddy current. The measurements can be stored in the same application, independent of the sheet material. With these functions, the PHASCOPE® PMP10 DUPLEX instrument is well suited for flexible measurements of the lacquer coatings on car bodies that are increasingly manufactured in composite construction, that is, in a combination of steel and aluminum sheet.